JSP + Servlet实现生成登录验证码示例

随机生成四位数验证码，包括汉字，数字，英文大小写。

1.Servlet类

package servlet;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import java.awt.geom.Line2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class PictureCheckCode extends HttpServlet {

private static final long serialVersionUID = 1L;

public PictureCheckCode() {
     super();
   }

public void destroy() {
     super.destroy();  
   }

public void init() throws ServletException {
     super.init();
   }
   /*该方法主要作用是获得随机生成的颜色*/  
   public Color getRandColor(int s,int e){
     Random random=new Random ();
     if(s>255) s=255;
     if(e>255) e=255;
     int r,g,b;
     r=s+random.nextInt(e-s);  //随机生成RGB颜色中的r值
     g=s+random.nextInt(e-s);  //随机生成RGB颜色中的g值
     b=s+random.nextInt(e-s);  //随机生成RGB颜色中的b值
     return new Color(r,g,b);
   }

public void doGet(HttpServletRequest request, HttpServletResponse response)
     throws ServletException, IOException {
   System.out.println("this is doGet method");
   this.doPost(request, response);

}

public void doPost(HttpServletRequest request, HttpServletResponse response)
     throws ServletException, IOException {

//设置不缓存图片
   response.setHeader("Pragma", "No-cache");
   response.setHeader("Cache-Control", "No-cache");
   response.setDateHeader("Expires", 0);
   //指定生成的响应图片,一定不能缺少这句话,否则错误.
   response.setContentType("image/jpeg");
   int width=80,height=35;   //指定生成验证码的宽度和高度
   BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //创建BufferedImage对象,其作用相当于一图片
   Graphics g=image.getGraphics();   //创建Graphics对象,其作用相当于画笔
   Graphics2D g2d=(Graphics2D)g;    //创建Grapchics2D对象
   Random random=new Random();
   Font mfont=new Font("楷体",Font.BOLD,16); //定义字体样式
   g.setColor(getRandColor(200,250));
   g.fillRect(0, 0, width, height);  //绘制背景
   g.setFont(mfont);          //设置字体
   g.setColor(getRandColor(180,200));

//绘制100条颜色和位置全部为随机产生的线条,该线条为2f
   for(int i=0;i<100;i++){
     int x=random.nextInt(width-1);
     int y=random.nextInt(height-1);
     int x1=random.nextInt(6)+1;
     int y1=random.nextInt(12)+1;
     BasicStroke bs=new BasicStroke(2f,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL); //定制线条样式
     Line2D line=new Line2D.Double(x,y,x+x1,y+y1);
     g2d.setStroke(bs);
     g2d.draw(line);   //绘制直线
   }
   //输出由英文，数字，和中文随机组成的验证文字，具体的组合方式根据生成随机数确定。
   String sRand="";
   String ctmp="";
   int itmp=0;
   //制定输出的验证码为四位
   for(int i=0;i<4;i++){
     switch(random.nextInt(3)){
       case 1:   //生成A-Z的字母
          itmp=random.nextInt(26)+65;
          ctmp=String.valueOf((char)itmp);
          break;
       case 2:   //生成汉字
          String[] rBase={"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"};  
          //生成第一位区码
          int r1=random.nextInt(3)+11;
          String str_r1=rBase[r1];
          //生成第二位区码
          int r2;
          if(r1==13){
            r2=random.nextInt(7);  
          }else{
            r2=random.nextInt(16);
          }
          String str_r2=rBase[r2];
          //生成第一位位码
          int r3=random.nextInt(6)+10;
          String str_r3=rBase[r3];
          //生成第二位位码
          int r4;
          if(r3==10){
            r4=random.nextInt(15)+1;
          }else if(r3==15){
            r4=random.nextInt(15);
          }else{
            r4=random.nextInt(16);
          }
          String str_r4=rBase[r4];
          //将生成的机内码转换为汉字
          byte[] bytes=new byte[2];
          //将生成的区码保存到字节数组的第一个元素中
          String str_12=str_r1+str_r2;
          int tempLow=Integer.parseInt(str_12, 16);
          bytes[0]=(byte) tempLow;
          //将生成的位码保存到字节数组的第二个元素中
          String str_34=str_r3+str_r4;
          int tempHigh=Integer.parseInt(str_34, 16);
          bytes[1]=(byte)tempHigh;
          ctmp=new String(bytes);
          break;
       default:
          itmp=random.nextInt(10)+48;
          ctmp=String.valueOf((char)itmp);
          break;
     }
     sRand+=ctmp;
     Color color=new Color(20+random.nextInt(110),20+random.nextInt(110),random.nextInt(110));
     g.setColor(color);
     //将生成的随机数进行随机缩放并旋转制定角度 PS.建议不要对文字进行缩放与旋转,因为这样图片可能不正常显示
     /*将文字旋转制定角度*/
     Graphics2D g2d_word=(Graphics2D)g;
     AffineTransform trans=new AffineTransform();
     trans.rotate((45)*3.14/180,15*i+8,7);
     /*缩放文字*/
     float scaleSize=random.nextFloat()+0.8f;
     if(scaleSize>1f) scaleSize=1f;
     trans.scale(scaleSize, scaleSize);
     g2d_word.setTransform(trans);
     g.drawString(ctmp, 15*i+18, 14);
   }
   HttpSession session=request.getSession(true);
   session.setAttribute("randCheckCode", sRand);
   System.out.println(sRand);
   g.dispose();  //释放g所占用的系统资源
   ImageIO.write(image,"JPEG",response.getOutputStream()); //输出图片
 }

}

2.web.xml配置

<servlet>
 <description>This is the description of my J2EE component</description>
 <display-name>This is the display name of my J2EE component</display-name>
 <servlet-name>PictureCheckCode</servlet-name>
 <servlet-class>servlet.PictureCheckCode</servlet-class>
</servlet>

<servlet-mapping>
 <servlet-name>PictureCheckCode</servlet-name>
 <url-pattern>/pictureCheckCode</url-pattern>
</servlet-mapping>

3.jsp页面输出验证码

<％@ page language="java" import="java.util.*" pageEncoding="utf-8"％>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>

<title>登录页面</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<script language="javascript">
 function myReload() {
   document.getElementById("CreateCheckCode").src = document
       .getElementById("CreateCheckCode").src
       + "?nocache=" + new Date().getTime();
 }
</script>

</head>

<body>
 <form action="loginServlet" method="get">
     <p class="font tdheight">
       验证码：<input type="text" name="checkCode"
         style="width:70px;height:35px;"> <img
         src="pictureCheckCode" id="CreateCheckCode" align="middle"
         style="margin-top:-10px;"> <br> <a href=""
         onclick="myReload()"
         style="font-size:12px;color:red;margin-left:156px;"> 看不清,换一个</a>
     </p>
     <br><input type="submit" value="提交"
           class="font" style="width:240px;height:35px;background:#f19e28">

</form>
</body>
</html>

4.后台Servlet判断验证码是否与输入一致

通过request.getParameter(“checkCode”)获取输入验证码，与session.getAttribute(“randCheckCode”)比较是否一致。

public void doGet(HttpServletRequest request, HttpServletResponse response)
     throws ServletException, IOException {

String code = request.getParameter("checkCode");
   HttpSession session = request.getSession();
   if (!code.equals(session.getAttribute("randCheckCode"))) {
     request.setAttribute("errormsg", "验证码不正确");
   }
   System.out.println(request.getAttribute("errormsg"));
 }

运行结果：

来源：http://blog.csdn.net/giving_bestself/article/details/59113140